The invention relates to a plate filter equipped with a plurality of filter plates that are movable by means of a closing device so as to be pressed against one another, with two adjacent filter plates in each case being in communication with one another by way of opening spacers and forming a filter chamber which is delimited by a continuous, raised sealing edge at at least one of the filter plates. At least one heavy liquid intake opens into the filter chamber and at least one of the filter plates delimiting the respective filter chamber is provided with a press membrane that can be charged by pressure medium. A preferably band-shaped filtering means is also provided which extends between each pair of adjacent filter plates.
In order to realize a large chamber volume and thus the correspondingly large cake thickness in plate filters of the above-described type, it is necessary to either configure the filter plates in the shape of a pot, in which case the bottom of the pot is formed by the press membrane and the filter surface is formed by the next-following filter plate disposed opposite the pot membrane and delimiting the filter chamber on the other side, as this is disclosed, for example, in German Patent DE 1,461,500. However, such a filter plate configuration has the drawback that, on the one hand, it has only one filter surface and, on the other hand, can be constructed only with the filter plates in the known horizontal arrangement since only with a horizontal arrangement of the filter plates the cake can be removed at the end of the filtration process.
In order to realize an increase in filter output in such plate filters, the filter plates have been designed to be effective bilaterally and the filter surface area has been enlarged in that a cake frame was placed between each pair of filter plates. The drawback of such cake frames is that it is not ensured, when the press is opened, that the filter cake drops out immediately and is transported completely out of the filter chamber by the filter band drawn through it. Remainders of filter cake that drop down later may remain lying on the filter band in the region of the sealing faces which leads to leakages in the entire system. Moreover, such cake frames require a high fill level so that the circulating filter band and the membranes or the membrane plates are not destroyed when pressure is applied. This can be realized only with easily filtrable suspensions. Finally, the provision of a cake frame requires very high closing forces so that a sufficiently high clamping force is applied to the cake frame which otherwise would be widened outwardly by the pressure of the suspension, leading to leakages and thus to malfunction of the entire press. The heavy liquid intake in such bilaterally filtering filter chambers would inevitably have to occur by way of the cake frame disposed between the two filter surfaces as this can be found, for example, in German Patent DE 2,043,156.